textproduct: Quad Cities

KEY MESSAGES

- Patchy dense fog will linger for the early morning commute today, largely north of I-80 along a stalled-out boundary.

- Shower and storm chances have increased for areas along and south of Interstate 80 this afternoon and evening, where some storms may be strong to severe.

- A period of mostly-dry and seasonal weather will be seen late this week and through the weekend.

SHORT TERM /THROUGH TONIGHT/

Issued at 128 AM CDT Wed Aug 19 2026

For the remainder of the overnight hours and into the Wednesday morning commute, there will be the chance for patchy dense fog. With a boundary north of the area slowly working south, this will act as a weak axis of convergence, allowing for fog to develop. We remain mostly cloudy overhead, which may limit some areas from developing fog, but areas along the boundary hold the best chance. Areas at best risk seem to be in northwest Illinois and some locations along Highway 20 in Iowa. Uncertainty remains on how far south this will spread, along with overall coverage.

Broad upper trof over the Great Lakes Region will continue to slowly push east through today and tonight, with weak bouts of energy continuing to pass overhead through the day today. The associated cold front will continue to make very slow southerly progress through this morning, essentially stalling out somewhere near the Interstate 80 to Highway 34 corridors by midday. Better moisture will be along/south of this boundary. Thus, with weak bouts of energy streaming overhead and the stalled out boundary in place, there will be the chance for showers/storms along and south of Interstate 80 this afternoon/evening. North of the Interstate, chances for storms are low, as a weak surface high pressure passes just north of the area, shunting things to the south. Highest PoPs will be along/south of the Highway 34 corridor, with 30-60% chances. Between Interstate 80 and Highway 34, we will generally see 20-40% chances. The overall trend in convective coverage has been upwards since mid-afternoon model runs, increasing our confidence in storm chances. A look at model soundings would also indicate that the environment south of the aforementioned boundary would be favorable for some organized convection, with deep layer shear around 35-45 KTs and instability around 2000-3000 J/kg. With this environment in place, there will be the chance for a few strong to severe storms as well. As such, the SPC has highlighted areas along and south of Highway 34 in a Marginal Risk, level 1/5, for severe weather. Primary threat will be severe wind gusts, with hail secondary. The main limiting factor in severe chances will be meager lapse rates. PWATs are also forecast to be between 1.50-1.75", which would be favorable for heavy rainfall in thunderstorms. Some short term models also indicated that there can be some localized training storms. This would lead to a localized flash flood threat as well, largely for areas along/south of Highway 34.

Going into the overnight hours, the better forcing will have moved out of the area. Thus, shower/storm activity should gradually decrease by mid-late evening. From there, we will be left with decreasing cloud cover, light winds, and temperatures cooling into the upper 50s in the north to mid 60s south.

LONG TERM /THURSDAY THROUGH TUESDAY/

Issued at 147 PM CDT Tue Aug 18 2026

Thursday through Tuesday... Assessment...low (20-30%) confidence on late week rain chances

The models have another front moving through the area in the late Thursday night through Friday evening time frame. Northwest flow aloft dominates well into next week so the overall moisture available for rain will be limited. The current model consensus is at a 20-35% chance of rain with the better chances generally along and north of I-80.

Outside of this time period, the prospects for rain is very limited with temperatures near normal.

AVIATION /12Z TAFS THROUGH 12Z THURSDAY/

Issued at 545 AM CDT Wed Aug 19 2026

Predominantly VFR with some areas of VLIFR to MVFR this morning north (KCID/KDBQ) in fog and MVFR/IFR this afternoon/evening south (KBRL) in shra/tsra.

A weak cold front bisects the area and extends from near KCID to south of KFEP at the start of the period. Areas of fog and variable conditions from VLIFR to MVFR were found along and north of the boundary near KCID and KDBQ terminals, and prevalent in the Mississippi River Valley and other low lying areas. This should lift and conditions improve by mid morning with some increase in northerly low level flow. Low level moisture and heating could foster a SCT-BKN MVFR stratus deck by mid morning through midday at both sites post-frontal before improvement to VFR. The cold front is expected to sag southward today and bring a northerly wind shift to KMLI 15z-18z, and KBRL 17z-20z. There is a low chance (20%) for a shra/tsra this morning at KBRL ahead of the front with better chances (40-60%) necessitating TEMPO mention this afternoon into early evening (21z-01z), as a disturbance over SD approaches. Light northerly flow is expected tonight, which should help keep any fog patchy.

DVN WATCHES/WARNINGS/ADVISORIES

IA...None. IL...None. MO...None.